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3
votes
1answer
57 views

How does `stdin` of linux work?

I know that stdin refers to standard input in linux, usually the keyboard. It can also be referred by file descriptor 0. So, which file descriptor does the (standard input) mouse refer to? Or is it a ...
3
votes
1answer
46 views

Does cat never read from terminal?

Chapter 43. Redirecting Input and Output of Unix Power Tools, Third Edition has to say this about cat command: Standard input (stdin) normally comes from your keyboard. Many programs ignore ...
2
votes
2answers
50 views

Decoding “prog > file 2>&1”

I am having some difficulty understanding the construct prog > file 2>&1. I have read that it means "Send stdout and stderr to file". But my question is how? I understand that prog > ...
23
votes
4answers
4k views

How to do nothing forever in an elegant way?

I have a program which produces useful information on stdout but also reads from stdin. I want to redirect its standard output to a file without providing anything on standard input. So far, so good: ...
7
votes
3answers
680 views

Why do some commands not read from their standard input?

I wonder what when we should use pipeline and when we shouldn't. Say for instance, to kill certain process which handling pdf files, the following will not work by using pipeline: ps aux | grep pdf ...
1
vote
1answer
46 views

Bash script and stdin

I am having a C program which requires to read from stdin. This is one of the requirements, and it cannot change. I have written a simple bash script that creates all the directories I want, handles ...
9
votes
2answers
243 views

How a piped shell programs balance their output/input rates? [duplicate]

Possible Duplicate: Bash while loop and reading from pipe I come from web programming background, and find myself interested in one peculiarity of using a local shell. I understand that ...
1
vote
1answer
27 views

Identify python script is waiting for a manual input

I'm writing a shell script which executes a Python script. The Python script halts for a manual enter to be provided. However, I don't wan't to have to press enter each time to the script. Instead, I ...
4
votes
2answers
335 views

using _< instead of < for stdin using bash

What is the difference between using _< and < for stdin when using process substitution. This is done using bash. Example: read bytes _< <(du -bcm random_iso.iso | tail -1); echo ...
3
votes
3answers
2k views

Bash script that reads filenames from a pipe or from command line args?

I want my script to read a bunch of filenames (which may have spaces) given either as a glob or from STDIN and do stuff with them. I've been able to read either way separately, but not combine them. ...
3
votes
3answers
243 views

stdin, stderr, redirection and logs

Is there a difference between those two lines ? /home/user/script.sh >> /home/user/stdout_and_error.log 2>&1 /home/user/script.sh 2>&1 >> /home/user/stdout_and_error.log ...
9
votes
3answers
462 views

tee stdout to stderr?

I'd like to send stdout from one process to the stdin of another process, but also to the console. Sending stdout to stdout+stderr, for instance. For example, I've got git edit aliased to the ...
3
votes
1answer
108 views

Piping commands, modify stdin write to stdout

echo Hello World | nano - | less I want to modify Hello -> Goodbye while in the the text editor. It does not have to be with nano. I am stuck with nano reading stdin but requiring me to write to a ...
6
votes
5answers
252 views

Is it possible to feed Open Office via STDIN?

I have an Open Office Spreadsheet document stored inside a bash variable. I want to do something like the following to feed Open Office via STDIN: echo "$openOfficeDoc" | ooffice But it doesn't ...
1
vote
1answer
393 views

Linux : how to redirect stdout & stderr to logger?

I have a program I need to run at startup, it has output on stdout and stderr that I want to redirect to the system log using the logger command. What I have in my startup script is thie: ...
2
votes
3answers
132 views

How do I make pasted shell commands invisible?

I'm using an AutoHotkey macro to run some shell commands, i.e. ^`:: SendInput set c=".cshrc-acheong"{ENTER} SendInput set v=".vimrc-acheong"{ENTER} SendInput foreach d ( /home/acheong /home/tcama ...
3
votes
2answers
400 views

Piped input to nano

Why does ls | nano - open the editor in Ubuntu but close the editor and save a file to -.save in CentOS? How can I get nano in CentOS to remain open when reading stdin?
3
votes
2answers
238 views

Is there a way to 'tee' input to a program or script?

I'm trying to find a way to use an input file for a program in such a way that I can also use stdin. For example, say I have a SQL script that creates a table. I invoke it like this: mysql -p ...
2
votes
3answers
320 views

Create a virtual file that is actually a command

Is there any way to create a virtual file, such that reading from the file actually reads from the stdout of a command; writing to the file is acually writing to the stdin of a command? So far I have ...
0
votes
2answers
49 views

file(1) command termination when using the -f - option

Say I'd like to use the file -f - command inside a script, and send some input using the stdin, when I'm finished I'd like to terminate it gracefully, but unfortunately I haven't found any way to do ...
6
votes
1answer
244 views

bash scripting - read tarball from stdin

I have a task I need to script that I feel should be stupidly simple, but I'm actually having a rather tough time. I have a short bash script that takes a specific type of application in tarball form ...
28
votes
4answers
7k views

Can I pipe stdout on one server to stdin on another server?

stdout on one CentOS server needs to be piped to stdin on another CentOS server. Is this possible? Update ScottPack, MikeyB and jofel all have valid answers. I awarded the answer to Scott because, ...
-5
votes
2answers
81 views

What is the utility of piping to `/dev/null`?

Seeing that /dev/null's utility isn't immediately obvious to me, what is the use of /dev/null piping?
1
vote
1answer
111 views

Bash Script which can direct stdin stream to program

I am trying to create a script capable of infinitely processing an incoming stream which is piped to it, and continuous producing an output stream which can be piped to something else something as ...
3
votes
1answer
70 views

What is the relationship between a program's output, standard output, and its file descriptors?

Let's assume that I am running wget which is downloading something. It's printing some text to my terminal and writes the downloaded data into a file. From a terminology point of view, what is the ...
4
votes
3answers
130 views

processing command output line by line, without mixing standard input

So, I have a problem very similar to Bash: How to read one line at a time from output of a command?, I am doing: while read path; do mplayer $path; done < <(find-me-random-mp3s) or ...
2
votes
1answer
3k views

nohup: ignoring input and redirecting stderr to stdout

I am starting my application in the background using nohup as mentioned below - root@phx5qa01c:/bezook# nohup java -jar ./exhibitor-1.5.1/lib/exhibitor-1.5.1-jar-with-dependencies.jar -c file ...
6
votes
2answers
204 views

Piping data to a process's stdin without causing EOF afterward

I have an executable that starts a user-interactive shell. I would like to, upon launch of the shell, inject a few commands first, then allow the user to have their interactive session. I can do this ...
3
votes
1answer
67 views

How can I make stdin always get consumed?

Some programs do not read from stdin (such as dmesg or adb logcat). I usually press Return a few times to provide a separation between log lines. When I interrupt the command directly in the shell, ...
1
vote
2answers
152 views

Is it possible to control xterm (or specifically a process that xterm has started) from another process?

If I start a process with xterm like this (where omxplayer is the process xterm is starting): xterm -fullscreen -fg black -bg black -e omxplayer -o hdmi -r %f Is it possible for me to write to ...
5
votes
3answers
1k views

Bash: interactive remote prompt

I have a script which connects to a remote server and check if some package is installed: ssh root@server 'bash -s' < myscript.sh myscript.sh: OUT=`rpm -qa | grep ntpdate` if [ "$OUT" != "" ] ; ...
3
votes
2answers
771 views

How to get mplayer to play from stdin?

Why doesn't this work? cat /dev/video1 | mplayer - If I could get that to work, then I could play & record video at the same time using 'tee' to feed mplayer and mencoder. I want to play live ...
1
vote
1answer
182 views

while loop is running only once?

I am trying to make a clip out of video file by playing it only for certain interval. make_mclip.sh #!/bin/bash mediafile=$@ mediafile_fullpath=$PWD/./$mediafile tmpedlfile=$(mktemp) mplayer ...
2
votes
3answers
107 views

How can a command have more than one output?

In this answer, at the very bottom, Gilles mentions that a command can have more than one output or input. Yes, there's cat foo bar | something, for having both foo and bar as inputs, and there's tee ...
2
votes
5answers
629 views

How to use filename arguments or default to stdin, stdout (brief)

I want to handle filenames as arguments in a bash script in a cleaner, more flexible way, taking 0, 1, or 2 arguments for input and output filenames. when args = 0, read from stdin, write to stdout ...
4
votes
3answers
427 views

Bash, name of the stdin file?

I have to write a bash script which will count symbols like "<" and ">" from stdin. For example: $ ./myscript.sh <example.html > - 20 < - 21 Found mismatching brackets! I did this: ...
8
votes
4answers
3k views

“openssl dgst -sha1” producing an extraneous “(stdin)= ” prefix and trailing newline

If you run this command on your Unix echo -n "foo" | openssl dgst -sha1 You will get this output: (stdin)= 0beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33 (followed by a newline). How can I force ...
3
votes
3answers
160 views

How to send part of the data through the pipe/file and later interactively?

I have a command I want to run, let's call it program. It is an interactive program similar to bash or python REPL. I want to start this program with some predefined input. I tried program << ...
0
votes
1answer
409 views

Using a file input as stdin for a shell script does not work

I have the following script code: test.sh echo "BEGIN" while read CMD <&1; do [ -z "$CMD" ] && continue case "$CMD" in start) echo "get_start" ;; ...
2
votes
1answer
112 views

How can I work around the program failing if there is *any* stdin?

For example, the following works fine: /usr/bin/program It produces some output, and gets to result. But if I invoke it like this: echo -n | /usr/bin/program or this echo -n | bash -c ...
6
votes
3answers
199 views

How to create merged input (stdin) for a program

Consider such script: echo a echo b echo c It will produce 3 lines and now I can run it like this: abc_script | real_program real_program will get in its input those 3 files. However, there is a ...
-1
votes
4answers
355 views

Ending Process Infinite Loop Input Redirection

Edit: I realized that the program I was trying to run had an infinite loop after scanning all my input. Then just prints out infinitely so it'll never read the EOF. It'll read the last input then go ...
0
votes
2answers
457 views

Redirecting stdin with stdout to file

So I have a program that takes in user input and outputs text based on the input. EDIT2: I want to create a script that runs a C executable and the script feeds the C program input from a file and ...
2
votes
2answers
136 views

Sending binary data to gets()

I have a victim program (with a buffer overrun vulnerability): it uses gets() to write into a fixed-sized buffer. Suppose I put shellcode into a file SC. Then I run $ ./victim < SC Input your ...
4
votes
4answers
803 views

Getting stdin from a named pipe

What I am trying to do is run python in a terminal window and redirect it's stdin from a named pipe. Then I write to the named pipe in another terminal and have that command execute on python. ...
5
votes
1answer
869 views

background process pipe-input

if i want to display "aaa" on screen: (1)$: echo aaa | cat ... works OK (2)$: echo aaa | ( cat ) ... works OK (3)$: echo aaa | ( cat & ) ... NOT working ...
6
votes
2answers
3k views

what is meant by connecting STDOUT and STDIN?

This is a newbie question. I'm reading a book, it says: Every process has at least three communication channels available to it: “standard input” (STDIN), “standard output” (STDOUT), and ...
3
votes
2answers
533 views

Simulate empty STDIN to detached command

i want to detach command either with 'command &' in the end, or with 'nohup command &', but it stops right after detaching it. command is little specific, if it receives eof on input, it ...
5
votes
3answers
537 views

Construct a command by putting a string into a tty

I managed to do this echo -n "command" > /dev/tty1 The letters appear, and the cursor moves, but they are "ghosts" - if you hit enter, nothing happens (they are not in stdin). Edit: In the ...
5
votes
1answer
36 views

IO and other shell commands when a program is not started by a terminal

I have several launchers on my desktop for various programs, and there is a "run in a terminal" setting for those launchers. When I check that setting, the program runs from a terminal, and logs its ...